Tinning oil composition and method of using same



' TINNING 01L COMPOSITION AND METHOD OF USING SAME John W. Nelson, Lansing, Ill. ,assignor to Sinclair Refining Company, New York, N.Y., a corporation of Maine No Drawing. Application September 27, 1956 Serial No. 612,362. 4 Claims. (Cl. 117-'-64) This invention relates to a novel composition of matter and in particular to a tinning oil composition consisting essentially of palm oil and pentatriacontenyl succinic acid anhydride for use in hot dip tinning operations.

In making hot dipped tin plate according to conventional practice, sheets of pickled steel are passed by means of rolls through a flux into a bath of molten tin and up through an eighteen-inch layer of hot palm oil, maintained at an elevated temperature, eg 450 F., floating on the tin. Three sets of rolls, operating in the oil, smooth and thin the tin coating. The palm oil serves to remove oxides that tend to form on the surface of the tin and also to retard atmospheric corrosion as well as assisting in handling during fabrication. Even though palm oil has been employed commercially in tinning operations, it has several disadvantages. The fiash and fire points of palm oil are low enough to create a fire hazard. It is quite volatile at tin pot temperatures and tends to increase in viscosity and polymerize with time at tin pot operating temperatures. In addition, a primary disadvantage is its foreign source, and the strategic and financial problems which thereby arise.

In accordance with my invention I have found that tinning oils can be prepared by blending pentatriacontenyl succinic acid anhydride together with palm oil. The acid anhydride is present in an amount sufiicient to increase the dewetting characteristics of the palm oil in hot dip tin plating Operations. Usually the acid anhydride is a minor amount up to about 50 weight percent of the total tinning oil and I prefer to use at least about 5% of the acid anhydride. The tinning oil compositions thus obtained function very satisfactorily in making hot dipped tin plate and are characterized by high flash and fire points, good stability at operating conditions and excellent activity or dewetting characteristics in removing objectionable metallic oxides and fiux residues as they form on the surface of the tin. In addition, the tinning oils prepared in accordance with my invention have the further advantage of partly replacing the conventional and expensive palm oil which must be imported. As used throughout the specification the term pentatriacontenyl succinic acid anhydride is intended to embrace the succinic acid anhydride as well as the corresponding succinic acid since both are interchangeable for the purposes of this invention.

A particular advantage obtained in hot dip tinning with tinning oils prepared by blending pentatriacontenyl succinic acid anhydride with palm oil is that the oil exhibits good acitvity and dewetting properties. Favorable tinning oils must necessarily have good dewetting properties. That is, the oil must be active in removing the objectionable tin oxides as they form on the surface of the tin. From the theoretical viewpoint an active, favorable tinning oil has a strong physical affinity for tin oxide and a powerful dispersing action in it. The combination of the cohesive force in the main body oil, the dispersibility of the oxide film in the oil and 2 the low friction between oxide and molten tin results the film being pulled under the body of oil and dispersed.

The layer of oil drains from the sheet until it is sufiiciently attenuated for oxygen to diffuse through it to the molten tin. Once the oil break has started it proceeds rapidly,

forinstantaneous oxidation of the molten tin exposed to air continually forces a negative contact angle between the tin and the oil.

In order to evaluate the activity and dewetting properties of tinning Oils the Petri dish test is employed. This test is suggested in Palm OilSubstitutes forHot Dip Tinning, in a preprint of a paper read before the general meeting of the American Iron and Steel Institute at New York, May 25-26, 1949, by'W. R. Johnson, L. C. Kinney and John M. Parks, of the Armour Research Foundation, Chicago, Illinois; jfAccording to this test; a Petri dishi's partly filled with'molte'n tin and an oil is added in just sutficient quantity to cover the surface. Inactive oils-defined as oils which remain in a continuous quiet film over the molten tinwet the tin and do not disperse or remove any tin oxide which may be present. Active oils break and expose an island of bright molten tin; they are in continuous motion, removing any oxide from the tin surface as fast as it forms. The oil remains in motion until it has become depleted at which time it creeps over the surface of the tin and behaves like an inactive oil.

The pentatriacontenyl succinic acid anhydride employed in the present invention can be prepared by known methods as, for example, by reacting pentatriacontene with maleic acid anhydride. Although somewhat lower molecular weight alkenyl succinic acid anhydrides exhibit activity as tinning oils, the possibility of their use in preparing satisfactory tinning oils has been found to be limited because of low flash and fire points which create fire hazards.

The following data tabulated in Table I illustrate the advantages obtained when using compositions prepared in accordance with this invention for hot dip tinning operations. In the Petri dish test which was employed, molten tin at 465 F. was covered with about 7 grams of various blends of palm oil containing from 0 to 50% by weight of pentatriacontenyl-17 succinic acid anhydride. As discussed above, if the oil is active it disperses the tin oxide and keeps the tin surface bright and visible. When the oil becomes inactive it covers the tin surface. The time required for the oil to become inactive is a measure of the efiiciency of the tinning oil. Palm oil, the traditional tinning oil, lasts about 25 to 35 minutes before it becomes inactive.

As shown above, the tinning oil compositions of this invention behave as active oils and readily remove any tin oxide that may form. Moreover, their activity is maintained over a considerable period of time and their flash and fire points are high enough to eliminate any fire hazards which might occur at tin pot operating temperatures of about 450 F. Thus, when as little as P Mer it-5&

ac d a h d de. said j amount varying from about to 50 percent by weight 'lbasedon theweightof the total tinning oil composition.

QS -Wei-ght-percent of pentatriacontenyl succinic acid an- 'hydride'is blended with palm oil, the'activity'characteristics of the palm oil are more than doubled while the flash and fire pointsare raisedappreciably higher than thos o pal p l- It is claimed: 7

1. A tinning 011 comppsitionjconsisting essentially'of 2. A tinning oil composition consisting essentially of a blend of palm oil and pentatriacontenyl suceinic anhydride being blended in an In hotdip tinning operations wherein freshly tinned jsteelplate is' contacted with a"bath'of a tinning oil main- ;tainejdat an elevated temperature, the step of contacting gthe tinned steel plate with a tinning oil consisting essentiallyof a blend of palm oil and pentatriacontenyl 'succinicacidanhydride, said anhydride being blended in an amount sufiicient to increase the dewetting characteristics of the palm oil in hot dip tin plating operations.

4. In hot dip tinning operations wherein freshly tinned steel plate is contacted with a bath of a tinning oil maintained at an elevated temperature, the step of contacting the tinned steel plate with a tinning oil consisting essentially of a blend'of palm oil and pentatriacontenyl succinic acid anhydride, said anhydride being blended in an amount varying from about 5 to percent by weight based on 'the weight of the total tinning oil composition.

References Cited in the file of this patent UNITED STATES PATENTS 

3. IN HOT DIP TINNING OPERATIONS WHEREIN FRESHLY TINNED STEEL PLATE IS CONTACTED WITH A BATH OF A TINNING OIL MAINTAINED AT AN ELEVATED TEMPERATURE, THE STEP OF CONTACTING THE TINNED STEEL PLATE WITH A TINNING OIL CONSISTING ESSENTIALLY OF A BLEND OF PALM OIL AND PENTATRIACONTENYL SUCCINIC ACID ANHYDRIDE, SAID ANHYDRIDE BEING BLENDED IN AN AMOUNT SUFFICIENT TO INCREASE THE DEWETTING CHARACTERISTICS OF THE PALM OIL IN HOT DIP TIN PLATING OPERATIONS. 